1. FIELD OF THE INVENTION
The present invention relates to a process for producing a cholesterol oxidase, more particularly, it relates to a process for producing a cholesterol oxidase by cultivating Schizophyllum commune IFO 4928 (deposited at the Fermentation Research Institute Foundation of 54, Jusan-Nishinomachi 4-chome, Higashiyodogawa-ku, Oska City, Japan) and extracting the desired cholesterol oxidase from the culture filtrate.
2. DESCRIPTION OF THE PRIOR ART
It is known that cholesterol oxidases can be produced from some kinds of bacteria, for example, Mycobacterium and Brevibacterium, or from Actinomyces. However, these cholesterol oxidases are unsatisfactory because they have too broad a substrate specificity. More particularly, in obtaining an enzyme that is active only on the hydroxyl group at the 3.beta.-position of cholesterols to oxidize the 3.beta.-hydroxyl group to a ketone group from conventional microorganisms by cultivation, extraction and purification, there are various technical problems which must be solved to put such processes to commercial use.
For instance, the enzymes obtained from Brevibacterium sterolicum are active not only on the 3.beta.-position but also on the 17.beta.-position of cholesterol, and their substrate specificity extends over a very wide range including cholesterol, cholestanol, dihydroergosterol, stigmasterol, testosterone, 5.alpha.-androstane-3.alpha.,17.beta.-diol and others. Their substrate spectra can be narrowed to a specific one only through several purification stages.
For practical use in evaluating or determining cholesterol with vital material such as tissue and serum, such a wide substrate specificity is not desirable. Therefore, various investigations have been made with a view to finding a cholesterol oxidase which has specificity only on the 3.beta.-position of cholesterol, and it has now been found, as a result of screening various bacteria, such as Eumycetes and Basidiomycetes, that a cholesterol oxidase having a highly distinctive substrate specificity can be obtained from a strain of Schizophyllum commune that has not hitherto been known.